The present invention relates to an ink jet head having a plurality of nozzles which discharge ink supplied from an ink supply unit, that is, an ink jet head suitable for use in a print head of an ink jet printer, for example, and a printer apparatus having the ink jet head.
The ink jet printer is a printer apparatus in a system that discharges drops of ink from an ink jet head having a plurality of nozzles to make to directly adhere the ink drops to a recording medium such as a printing paper or the like. For instance, the ink jet printer prints on a printing paper by conveying the printing paper in a direction perpendicular to a direction of moving the ink jet head while reciprocally moving the ink jet head in a direction of the width of the printing paper.
FIGS. 34 and 35 are diagrams illustrating the structure of a known ink jet head. FIG. 34 is an exploded perspective view for illustrating the structures of essential parts of a known ink jet head disclosed in Japanese Patent Laid-Open Publication No. H6-99580. FIG. 35 is a diagram for illustrating a wiring method in the ink jet head.
The known ink jet head is disclosed in, for example, Japanese Patent Laid-Open Publication No. H6-99580, which comprises a nozzle plate 310 in which a plurality (64 in the drawing) of nozzles 312 are cut and formed, and a substrate 311 having a plurality (64 in the drawing) of ink chambers 313 formed correspondingly to the respective nozzles 312, as shown in FIGS. 34 and 35.
In the substrate 311 formed are an ink supply port 318 which communicates with an ink tank not shown, and ink supply channels 314 which link and connect the ink supply port 318 to ink chambers 313.
The nozzle plate 310 is adhered to a surface on a side (the upper side in FIG. 34) where the ink chambers 313 on the substrate 311 are formed. By adhering the nozzle plate 310 to the substrate 311, ink can be filled inside each of the ink chambers 313 and the ink supply channels 314. The ink supplied from the ink tank can be thereby supplied to each of the ink chambers 313 through the ink supply channel 314.
In the substrate 311, a surface of each of the ink chambers 313 opposite to the nozzle plate 310 is formed by a vibrating plate not shown, so that each of the ink chambers 313 is formed as a space sandwiched between the vibrating plate and the nozzle plate 310. A peizoelectric element 315 is disposed on the opposite side (the lower side in FIG. 34) of each of the vibrating plates to the ink chamber 313. The vibrating plate and the piezoelectric elements 315 form a bimorph layered body.
An individual electrode (not shown) is formed on a surface (the lower side in FIG. 34) of each of the piezoelectric elements 315 opposite to the vibrating plate. The individual electrodes are electrically connected to FPCs (Flexible Printed Circuit Boards) 316A through 316D by wire bonding using wires 317. Incidentally, the above vibrating plate is made of a member having conductivity, as well.
Each of the FPCs 316A through 316D is connected to a printing signal generator through a connector or the like not shown. A printing signal is transmitted from the printing signal generator to each of the individual electrodes and the vibrating plates, so that each of the piezoelectric elements 315 applies pressure to the ink chamber 313, and ink is discharged from each of the nozzles 312.
Since the individual electrode of each of the piezoelectric elements 315 is connected to the FPC 316A, 316B, . . . , 316D or by wire bonding using the wire 317 in the known ink jet head, it is necessary to secure a space to wire the wire 317 by wire-bonding on the upper side of each of the individual electrodes, that is, on the opposite side to a surface of the substrate 311 to which the nozzle plate 310 are adhered. This leads to problems that the packaging density of the nozzles 312 cannot be increased, and the size of the ink jet head cannot be decreased.
Since the wires 317 are connected by air wiring (wire bonding), short circuit might occur between the wires 317, and the piezoelectric element 315 or the like might be damaged when each of the piezoelectric elements 315 and the FPC 316A, 316B, . . . , or 316D are connected by wire bonding.
In the ink jet head in a multiple nozzle structure having plural rows of nozzles, it is necessary to form a row of electric contacts for each row of the nozzles (individual electrodes), and to connect the wires 317 for each row of the electric contacts. This leads to a low fabrication efficiency of the ink jet head.
Further, the wire bonding has a limitation of reduction the contact pitch. For example, when the contact pitch is not larger than about 60 xcexcm (not less than 450 dpi as a nozzle pitch), the fabrication stability might decrease in case of mass production.
A method of directly soldering the FPCs 316A through 316D to the individual electrodes is also generally known, which has the similar problems that the above method employing wire bonding has.
In the light of the above problems, objects of the present invention are to facilitate connecting to external connection wiring members, to improve the fabrication efficiency and the reliability, and to decrease the size of the ink jet head and the printer apparatus.
The present invention therefore provides an ink jet head having a plurality of nozzles discharging ink supplied from an ink supply unit comprising a head main body including a plurality of pressure chambers provided for the nozzles, respectively, in which ink is filled, and a plurality of pressure units provided for the pressure chambers, respectively, each of the pressure units applying pressure to the pressure chamber to discharge the ink in the pressure chamber from the nozzle, an individual electrode provided for each of the pressure units to drive the pressure unit, at least one contact connected to an external connection wiring member supplying a signal for controlling the pressure unit, and a wiring pattern formed into a thin film to electrically connect the individual electrode to the contact.
Accordingly, each of the individual electrodes and the external connection wiring member can be electrically connected readily, which improves the fabrication efficiency of the ink jet head. Further, the individual electrode and the contact can be electrically connected certainly, which improves the reliability. Still further, a space for wire bonding (air wiring) becomes unnecessary, which allows reduction of the size of the ink jet head and the printing apparatus.
Since a wiring pattern electrically connecting the individual electrode to the contact is formed into a thin film, a space above the individual electrode for laying a wire connecting the individual electrode to the external connection wiring member becomes unnecessary. Hence, freedom can be given to the shape of the ink jet head, and the size of the ink jet head can be reduced.
The individual electrode, the contact and the wiring pattern may be integrally formed into a thin film on the same surface from the same material. This allows the ink jet head to be fabricated at a low cost and readily.
The ink jet head may further comprise a joint formed to project from the head main body so that the ink supply unit is mounted to the head main body. It is thereby possible to mount the ink supply unit to the head main body readily and certainly, and improve the rigidity of the head main body.
The head main body may be formed on a substrate, and the joint may be formed as a remaining part of the substrate on the head main body by partially removing the substrate from the head main body. It is thereby possible to form the joint readily and certainly in the course of substrate forming, thus the fabrication cost can be decreased.
The joint may be formed to enclose the individual electrodes on a surface on which the individual electrodes, the contacts and the wiring patterns are formed, and the contacts may be disposed outside the joint. Alternatively, the joint may be formed to enclose the individual electrodes on a surface on which the individual electrodes are formed, and to project outward from a periphery of the head main body, and the contacts may be arranged outside the periphery of the head main body on the side of the joint. It is thereby possible to increase the rigidity of the head main body, and readily connect the external connection wiring member to the contacts.
The joint may function as a positioning unit positioning the external connection wiring member to the contact. It is thereby possible to certainly connect the external connection wiring member to the contact, and improve the reliability.
Positioning of the external connection wiring member to the contact may be performed by fitting an end surface of the external connection wiring member to an outer peripheral surface of the joint. It is thereby possible to certainly position the external connection wiring member to the contact.
A positioning unit for positioning the external connection wiring member to the contact may be formed as a remaining part of the substrate on the head main body by partially removing the substrate from the head main body. It is thereby possible to certainly position the external connection wiring member to the contact, and readily form the positioning unit.
Positioning of the external connection wiring member to the contact may be performed by fitting the positioning unit into at least one positioning hole formed on the side of the external connection wiring member. It is thereby possible to certainly position the external connection wiring member to the contact.
The external connection wiring member may be an FPC (Flexible Printed Circuit Board), and may be electrically connected to the contact by the use of a TAB (Tape Automated Bonding) technique. The pressure unit may comprise the individual electrode, a vibrating plate forming a part of the pressure chamber and a piezoelectric element driving the vibrating plate to apply pressure to the pressure chamber. It is thereby possible to certainly realize the present invention.
The present invention also provides a printing apparatus comprising an ink jet head having a plurality of nozzles discharging ink supplied from an ink supply unit comprising the ink jet head including a head main body including a plurality of pressure chambers provided for the nozzles, respectively, in which ink is filled, and a plurality of pressure units provided for the pressure chambers, respectively, each of the pressure units applying pressure to the pressure chamber to discharge the ink in the pressure chamber from the nozzle, an individual electrode provided for each of the pressure units to drive the pressure unit, at least one contact connected to an external connection wiring member supplying a signal for controlling the pressure unit, and a wiring pattern formed into a thin film to electrically connect the individual electrode to the contact.
Accordingly, each of the individual electrodes and the external connection wiring member can be electrically connected readily, which allows improvement of the fabrication efficiency of the printing apparatus. Each of the individual electrodes and the contact can be electrically connected certainly, which allows improvement of the reliability. Since a space for wire bonding (air wiring) becomes unnecessary, the size of the printing apparatus can be reduced.